Field of the Invention
The present invention relates to a panoramic image generation method for generating a panoramic image from a plurality of captured images.
Description of the Related Art
As a panoramic image generation method, Japanese Patent Application Laid-Open No. 2001-136514 discusses a technique for dividing an entire area that imaging apparatus can photograph by oscillation into a plurality of areas, performing projective transformation of captured images of each area, and connecting them.
As a synthesis method of a privacy mask, Japanese Patent Application Laid-Open No. 2001-69494 discusses a technique for generating a privacy mask having a position and a size according to an oscillation angle of the imaging apparatus, and superimposing the mask to a captured image.
However, there is a possibility that the quality of the panoramic image may be deteriorated depending on a position on which the captured image is processed.
For example, in a case that a privacy mask area is overlapped between a plurality of captured images for generating a panoramic image, there is a possibility that a privacy mask image is shifted at a connected part when a panoramic image is generated by performing projective transformation on the plurality of captured images on which the privacy mask image is superimposed.
Further, for example, in a case that a privacy mask area (hereinafter referred to as the mask area) is not overlapped between a plurality of captured images, there is a possibility that an area on a panoramic image, which should be a mask area, does not become the mask area. For example, a case is described in which a position of a mask area is managed by information of a pan angle and a tilt angle of a camera corresponding to a center position of the mask area, and a size of the mask area is managed by information about a width and a height.
In this case, if a mask image is superimposed on each of the plurality of captured images based on the pan angles and the tile angles at the time of capturing the plurality of images; and then a panoramic image is generated, there is a possibility that an area which should be a mask area is shifted from an area on which the mask image is actually superimposed. This phenomenon is particularly remarkable at an area having a large tilt angle (in general, an upper area of a panoramic image). This is because as the tilt angle is large, a moving direction of an image capturing direction of the camera according to pan control becomes different from a just horizontal direction.
In addition, when an imaging apparatus including an on-screen display function generates a panoramic image, there is a possibility that an image quality of the panoramic image is deteriorated. The on-screen display function superimposes an on-screen image, such as an imaging date/time and an imaging place, on a captured image. More specifically, there is a possibility that an unnecessary on-screen image is superimposed at a connected part of the captured images on the panoramic image depending on a superimposition position of the on-screen image.
FIG. 5 illustrates an example of a panoramic image generated by the above-described method. In FIG. 5, shadow areas illustrate a privacy mask image and areas indicating a date/time on the below side illustrate on-screen images. As illustrated in FIG. 5, depending on the superimposition position of the privacy mask image on each captured image, there is a possibility that an irregular area and a partially missed area generate at an edge part of the privacy mask image. Further, depending on the superimposition position of the on-screen image on each captured image, there is a possibility that a not-distinguishable unnecessary on-screen image is superimposed.